One of the biggest threats to the sustainability of the world’s oceans is the over-exploitation of marine resources. To manage this threat, which is largely a product of over-fishing and other extractive activities, governments restrict the activities that can occur in their marine areas. These restrictions include regulation of fishing effort in certain locations, or the creation of no-take zones (areas where fishing or other extractive activities are prohibited).

Spatial optimisation models can help policy makers plan the best use of marine areas amongst these different activities. Each activity will carry different opportunity and management costs while producing different levels of ecological or economic benefit. The data that is available on the spatial distribution of these benefits and costs can be incorporated into spatial optimisation models to determine the best allocation of area amongst the different activities. The aim is to maximise conservation or economic value; while meeting some objective such as a conservation target or economic constraint.

Chilean TURF

In Chile, marine species such as the Chilean-abalone or ‘loco’ are managed through a Territorial User Rights for Fisheries (TURF) program (see the box on TURF and conservation). This gives artisanal fishers property or user rights over a defined coastal area. To be part of this program organisations must comply with limits on total allowable catch, carry out annual population surveys for key species in their management area, and be responsible for all management costs.

Management costs in Chile are all about enforcement – the costs of monitoring to deter poachers. Research has shown that species’ abundance levels are higher in enforced areas; a trend attributed to decreased catch.

In this analysis we collected data on the costs of enforcing the existing TURF program and no-take areas in Chile to develop a spatial distribution of enforcement costs across an area in the central marine region (Figure 1). We then incorporated these costs into a spatial optimisation model to determine the best allocation of the area amongst activities like fishing, no-take areas, and open access areas with no management (Davis et al., 2014). Our objective was to understand how the revenue of artisanal fishers in Chile could be maximised while meeting conservation targets.

“There are net benefits from enforcing marine areas; fisher revenue was higher when fishing areas were enforced to prevent poaching. We also found that enforcement was important for conservation.”

We used data on the equilibrium abundance levels of five commercially exploited species – two invertebrates and three reef fish – to estimate potential fisher revenue under five different zones. Each zone allowed different activities (fishing or no fishing) and had a specific catch restriction. These zones were: open access (which had no restriction on what activities could occur in the area); TURF fishing areas; no-take areas where extractive activities were prohibited; and TURF and no-take zones which were enforced and therefore incurred an enforcement cost. We restricted the catch that could occur in TURF areas to reflect current catch limits in Chile, assumed no catch in no-take areas, and matched catch in open access areas to the exploitable stock level of each species – the proportion of the population large enough to catch.

Figure 1. Enforcement costs in the central marine region of Chile; fishing organisations are indicated. Inset describes location of study area on the Chilean coast.

Best management of the study area

We found that to make the most money for fishers (maximise fisher revenue), the best strategy was to allocate the whole study area to the enforced-TURF zone (Figure 2). This strategy changed only slightly when conservation targets were included; under this second scenario optimal spatial management included no-take areas as well.

Further analysis of the data allowed us to ascertain how cost-effective enforcement was – we wanted to know whether the higher abundance found in enforced zones translated into net benefits when you considered how much it cost to enforce. What we found was that for every $1 (2012 USD equivalent) spent enforcing, fisher revenue increased between $4 and $9 – a massive return on investment.

Enforcement has net benefits

Our analysis demonstrated that there are net benefits from enforcing marine areas; fisher revenue was higher when fishing areas were enforced to prevent poaching. We also found that enforcement was important for conservation; much higher conservation targets could be met if marine areas were enforced. Our results demonstrated that investment in management, which provides conservation benefits, could be justified by greater economic returns for fishers.

Although our research demonstrated that enforcement of fishing areas is in fishers’ best interests, roughly one third of the TURF management areas currently allocated in Chile are not being enforced. This contradiction may be explained by several factors – including lack of money or time on the part of fisher organisations.

Comments from fishers in the study area indicate that enforcing represents a significant safety risk for guards, and that it may be associated with social costs. Many poachers will be members of the local community and fishing has traditionally been a safety-net for these community members when other income streams have failed.

Our results have indicated that there can be large net benefits from the enforcement of marine management areas: fishers’ income was increased, and higher species’ abundance levels were observed when marine management was enforced. Understanding what influences the decision of artisanal fishers in Chile to enforce their TURF management areas should be a high priority for the future.

Figure 2. Optimal spatial allocation of the study area amongst different management zones with (left), and without (right) a conservation target.

TURF and conservation

Territorial user rights for fisheries (TURF) has the potential for significant conservation outcomes. Agreements on TURF assign spatial user rights to groups of fishers for the sustainable management of a species or group of species. The rationale for establishing user rights is based on the theory of common property, which assumes that securing access and sharing control over resources can create incentives for sustainable institutional arrangements among fishers, who will then manage and harvest collectively and sustainably. In addition, TURFs are expected to contribute to sustainability by increasing fishers’ likelihood of compliance.

Chile has a national TURF policy. Through this policy the undersecretary of fisheries assigns exclusive-access diving rights to fisher organizations. To be granted a TURF, Chilean artisanal fisher organizations must develop, with the technical assistance, 5-year management plans, which must be approved by the undersecretary of fisheries. Fishers are also responsible for surveillance and enforcement of anti-poaching measures.

The first TURF in Chile was established in 1997 and currently there are 707 TURFs. They apply to over 1100 km2 of shallow coastal ecosystems and are on average 100 ha and 4–10 km apart. In Chile, TURF management plans consider economically important benthic species, such as the loco, key-hole limpets and sea urchins. In areas with TURF agreements, extractions of species not included in the TURF management plan are forbidden.

In areas in Chile with well-enforced TURF agreements the density and size of managed species has increased substantially relative to open-access areas.